A pregnant woman is chased by a man who tries to kill her and the baby. Without knowing the details, Ji Chun Deuk, the treasurer of Jeonokseo happens to take care of the baby girl whose mother dies as soon as she gives birth to her. This girl grows up in the prison with the name Ok Nyeo.

Ok Nyeo is invited to tell Yoon Won Hyung and Jung Nan Jung’s fortune and receives silk clothes in return. On her way back to Jeonokseo, she gets kidnapped by Mount Daedeok bandits. They take her for Lord Yoon’s daughter and plan to save their leader who is due to be executed soon.

Ok Nyeo happens to help a female prisoner switch herself with someone else who would do anything for money. It turned out to be an old lady, and during their mission, Ok Nyeo hears about why she was born in Jeonokseo and how her mother died.

Although Ok Nyeo applied to become a warden at the Police Bureau, she fails because she's overqualified. While she’s thinking of becoming a spy instead, an envoy from Ming arrives and announces that he will have to get to the bottom of how and why the former king died.

Ok Nyeo is visited by the Chief of the Police Bureau and asked to decide if she wants to become a spy. She undergoes a series of training to become skillful enough to complete a mission. Meanwhile, Tae Won works towards his goal of taking revenge on Jung Nan Jung, and Queen Munjeong personally asks Tae Soo to accept her deal.

After passing the final test, Ok Nyeo officially becomes a spy. Kang Sun Ho assigns her a mission, which is to steal the letter from Oh Jang Hyun. On her mission, she encounters two people, Tae Soo and Tae Won. Tae Soo is surprised to find out she is in the same mission as him, and becomes worried about her safety.

Ok Nyeo and Tae Soo’s mission to assassinate the envoy and to steal the letter is carried out. However, Yoon Won Hyung has an ulterior motive, which is more important than killing the envoy. When Ok Nyeo barely makes it back to Joseon, she is arrested and requested to admit to all the charges brought against her because she is a spy.

Ok Nyeo is transferred to the Capital District Office Prison as a felony. Everyone, including Tae Won, is trying to find out why she’s imprisoned and how they can help her but it seems that everything is kept secret. Meanwhile, the reason why Tae Won yearns to take revenge on Jung Nan Jung is revealed.

With the help of Ki Choon Soo, Ok Nyeo hides in a secret and safe place. But the words get out, and Lord Yoon is informed of her whereabouts. Queen Munjeong sees how desperate her brother is to conceal the truth, so she continues to look into the death of Park Tae Soo.

Tae Won takes Ok Nyeo to a safe place as she’s still on the run. Lord Yoon tries his best to catch her while Queen Munjeong is also trying to meet with her. Ok Nyeo is caught in the end and is taken to the Palace and tells the Queen everything that happened.

After listening to Ok Nyeo, Queen Munjeong order that Ok Nyeo be pardon and Yoon Won Hyung to be removed from all his posts. Tae Won and Ok Nyeo plan to use this chance to get back at Jung Nan Jung, and another incident occurs inside Jeonokseo.

To turn the table around, Jung Nan Jung spreads a false rumour that Lee Myung Woo and the people he bribed were trying to plot treason. Lord Yoon is released from Jeonokseo to take care of the incident, and Tae Won, the last person Lee Myung Woo met before he died, is taken to the Police.

As soon as Gong Jae Myung is released, he goes to Lord Yoon and tells him that Tae Won is his illegitimate son and that he is being interrogated at the Police Bureau because of the frame set up by Jung Nan Jung. Meanwhile, someone is trying to kill Myung Seon to get rid of the evidence that they attempted to murder the Anguk-dong lady.

The lady in Anguk-dong dies in the end, which makes Tae Won and Ok Nyeo furious. Moreover, Nan Jung receives the Revered Lady title from Queen Munjeong and becomes Lord Yoon’s official spouse. While the whole country is starving due to the famine, Nan Jung’s grain storage is the only thing that is full. Tae Won and Ok Nyeo are planning to use this as a chance to get back at Nan Jung and Lord Yoon.

To get rice to feed the prisoners in Jeonokseo and to save the poor suffering from the famine, Ok Nyeo and her people gather the ideas to swindle Jung Nan Jung. They throw the bait at her, using her greed, and it seems like she has taken it. Meanwhile, Ji Heon realises that he was adopted and tries to listen to what Ok Nyeo has to say about his birth parents.

Ok Nyeo’s plan to con Jung Nan Jung doesn’t seem to be working out in the beginning when Jung Nan Jung locks up Woo Chi and tortures him. However, with the help of Woo Chi’s friends, the team succeeds eventually. The prisoners in Jeonokseo are able to eat fully after a long time.

To make Jeonokseo run smoother, Ok Nyeo comes up with another great plan: making prisoners work to provide salt. An auction to supply to the Price Policy Division is scheduled. However, Jung Nan Jung’s organisation has been supplying salt exclusively. Will Ok Nyeo and Tae Won be able to compete against her and succeed?

As soon as she finds out Lord Yoon had been seeing Tae Won, Jung Nan Jung becomes furious and tries to beat Tae Won at the salt supply auction at all costs. She hires men to find out how much Sir Gong’s bidding price will be and offers an unbeatable price despite a huge loss that would be incurred later on, just to beat Tae Won.

To come between Tae Won and Lord Yoon, and to take revenge on Sir Gong, Lady Jung steals the secret ledger of Jeonokseo. Officer Sung cannot refuse to carry out the investigation because of the evidence given to him. Ok Nyeo, Chief Jung, Tae Won and Sir Gong will have to stand a trial for bribing each other.

Lady Jung realises she should have gotten rid of Ok Nyeo a long time ago. She asks Lord Yoon to make her become a slave in return for setting Tae Won free. Meanwhile, Ok Nyeo’s friends are so worried she might become a slave that they plan to help her escape. However, she doesn’t want to inconvenience others who are left behind, hence she stands the trial.

Despite Ji Heon’s effort, Ok Nyeo is sent away to a provincial office as a slave as Lord Yoon and Lady Jung wanted. Although Tae Won and Jae Myung are released, Tae Won becomes furious to hear Jae Myung made a deal with Lady Jung, and leaves the organisation. Deeply heart-broken, Ok Nyeo’s friends try to come up with a plan to save Ok Nyeo from becoming a slave.

On her way to Haeju with other prisoners, Ok Nyeo’s group gets attacked and kidnapped by a gang of bandits on Mount Chilsung. The news is heard in Hanyang, which makes everyone think that Ok Nyeo is dead. However, she manages to free herself and the other girls from the bandits on their way to Yongdae Dock, right before they are sold to the Ming slave traders.

k Nyeo finds out that she may have to be a slave that entertains officials in Haeju. Ji Heon and Ok Nyeo try to come up with a plan to find a way out. Meanwhile, Lord Yoon wakes up and apologises to Tae Won for all the wrong things he did. He offers to ally with Tae Won to keep Nan Jung in check together.

Ji Heon and Ok Nyeo go on a trip together to look for what Tae Soo left for his grandson. Meanwhile, to exercise his authority as Chief of Price Policy Division, Tae Won attacks Sung Hwan Ok, the richest man in Kaesong. An unfortunate event occurs, which puts Ok Nyeo, Ji Heon and Tae Won in a very complicated relationship altogether.

To pray for a good year ahead for fishermen, a ritual ceremony is to be held at Haeju. Ok Nyeo does not miss her chance and thinks of a way to get out of servitude. Meanwhile, Tae Won persuades Nan Jung that he has moved on from wanting to take revenge on her to wanting to make up.